Muffler for gas engines



i; W, HALL MUFFLER FOR GAS ENGINES Filed Feb. 9,, 1926 INVENTOR sY k m ATTORNEY Patented Dec. 27, 1927.

UNITED STATES CHARLES WARD HALL, OF

MUFFLER FOR Application filed February This invention relates to a muflfler for gas engines-more articularly for aircraft engines, althoug not necessarily limited thereto.

One object of the inventionis to provide 'a mufiier which will silence, or largely silence, the noise of the engine exhaust and at the same time will induce a strong suction during the latter part of the scavenging stroke and thereby more completely remove the burnt gases and so permit of a less diluted fresh charge. 7

A further object is to provide a mufiier which is simple in construction, and hence may be produced at low cost, and is also capable of being readily cleaned of deposited carbon.

With these objects in view my improved muffler comprises, as its essential parts, a Venturi tube, an annular chamber which surrounds the venturi and is connected therewith by openings 'in its walls to the rear of the throat, and an inlet which at its outer end is adapted for attachment to the engine exhaust port and thereby to support the muiiier and which spreads the exhaust gases and delivers them into the annular chamber tangentially in a thin strea'rn substantially from end to end thereof.

The volume of the muffler is preferably from two-thirds of to the full volume of the engine cylinder. The inlet, which at its outer end or intake is of the same size as the exhaust port of the engine, widens rapidly therefrom in one dimension and in-the other dimension narrows slowly to a slit, with 'a large and continuous increase in cross-sectional area, the discharge slit through which it connects longitudinally with the annular chamber having an area preferably of from one and one-half to two and one-half times the area of the intake. The urmer or outer side of the inlet is preferably tangent to the outer cylindrical wall of the chamber, and its opposite inner side would, if extended, intersect the same. The annular chamber, formed'between this outer wall andthe Venturi tube and having an area of from two and one-half to four times the area'of the PATENT OFFICE.

LARCI-IMONT, NEW YORK.

eas ENGINES.

e, 1926? Serial No. 86,977.

ly in a short cylindrical lip,a short throat with parallel or preferably slightly rounded sides, and a much longer and more slightly tapering rear section which is perforated by a number of holes and which, terminating in a short cylindrical lip, is extended by the vrearconical stamping to, the outer casing at its rear end. Suitable proportions for, the venturi, for the use here intended, area mouth section with intake of from two to five times the area of the throat and with the angle of its cone not over thirty degrees, and a rear section which is from five to eight throat diameters in length to the point where it connects with the conical stamping and at the extreme rear end of the muffler has an area of from five to twelve times the area of the throat.

The greater the ratio of the entrance and of the discharge areas of the venturi to the area of the throat, the greater will be the suction produced for a given speed. As usual in any venturi the reduction in pressure is greatest at the throat, but is well pronounced throughout all the rear section. Therefore, an open throat as the only exhaust outlet would produce the highest possible suction. This, however, while desirable as increasing the engine power, tends to a too rapid discharge of the burnt gases to act as an effective mufiier, since the maximum reduction ofnoise results from the slowest and most diffused exit of these gases. I accordingly provide muiflers of diiferent types merely by varying the perforations connecting the outer chamber with the Venturi tube. For one type, a mufiier which will aiford a maximum of silencing, there. may be some two hundred to two hundred and thirty small holes, having an aggregate area of from one and one-fourth to one and threefourths the area of the inlet discharge slit, which are evenly distributed over the rear section of the venturi. The other type, in which the venturi is perforated at or near the throat onlyand by a few, approximate 1y a dozen, larger openings aggregating in area three-fourths to one and one-fourth the area of the inlet discharge slit, is less perfect as a silencer but is much more effective in exhausting theburnt gases from the engine cylinder. I

' A factor contributing to the efiicienc of the muflier as a silencer is the substantially cylindrical form of the outr casing or muffler body and the tangential entrance pro ALI itself produces a minor secondary swirl in the exhaust for each of the small perforations, resulting in a ery quiet discharge.

By removing three or four small bolts or rivets by which the forward end of the venturi is joined to the forward conical stamping, the venturi may be pushed out of the casing and the whole muffler readily cleaned of carbon without removal from the engine to which it is attached.

One practical embodiment of the two different types of mufflers is shown, by way of illustration and not of limitation, in the accompanying drawings, in which Figure l is a top or plan view of a muffler of maximum efficiency as a silencer with parts of the outer casing and of the inner /enturi tube broken away; Fig. 2 is a side view of the same, also with a portion of the outer casing broken away; Fig. 3 is a view showing the mufiler partly in rear end elevation and partly in section on the line 3 8 of Fig. 1; Fig. 4 is a view, in longitudinal secton on the line 4 l of Fig. 5, of a mulller of the second type, effective in exhausting the burnt. gases; and Fig. 5 is a transverse section of the same on the line 5 5 of Fig. l.

Referring to the drawings, the Venturi tube proper comprises an imperforate conical forward end or mouth section 11, which terminates in a-short cylindrical extension or lip 12, a short throat 13, and a rear section 14 which also terminates in a short cylindrical lip 15, ofthe same diameter as the lip at the forward end. The rear part of the tube shown in Figs. 1 to 3 is perforated by a large number of small evenly distrib uted holes 16, and as shown in Figs. l and 5 is provided with a. few larger openings 16 grouped together close to the throat. The venturi is mounted within and secured coaxially of the cylindrical outer casing l? by means of the two like conical stampings 18 18, provided at their ends with short cylindrical extensions or lips 19 and 20, one of which stampings is fitted at its smaller forward end upon and secured, preferably by three or four small bolts 21, to the cylindrical lip at the mouth of the venturi and at its rear larger end by rivets within the forward end of the casing, closing the forward end of the annular chamber 22, and the other stamping is fitted at its smaller forward end by a slip joint upon the cylindrical lip at the rear end of the venturi and at its larger rear end is riveted to the rear end of the casing, forming a rearward extension of the Venturi tube which closes the rear end of the cham-' her. The casing 17, as shown, is shaped up from a sheet of metal which is rolled up from one of its sides 23, which forms one side of a longitudinal opening, to nearly a complete cylinder and is left extending at a tangent from the other side of such longitudinal opening. This integral extension of the casing wall suitably shaped up, forms the upper or outer side 24 of the muffler inlet and at its flanged edges 25 is riveted or otherwise suitably secured to the flanged edges 26 of the opposite inner inlet sidepiecc 27, which is shaped up from a sepa rate sheet of metal and at its inner end 28 extends inwardly somewhat beyond and is riveted to the flattened and slightly inturned side 23 of the casing. Where, as in the type of muffler shown in Figs. l: and 5, the outer chamber is connected with the interior of the venturi only near the throat of the latter, the extended inner end of the lower inlet side-piece, within the chamber, is preferably curved outwardly as at 28', opposite the perforations in the Venturi tube, to deflect the exhaust gases away from these perforations and towards the ends of the chamber. The outer ends of the two inlet side-pieces are fitted in any suitable manner for attachment to the exhaust port of the engine for which the mulfler is designed-as shown for example, for attachment to the oval exhaust port of a Wright engine, by providing them with outwardly projecting flanges 29 29 and building them up as at 30 with torch and wire to give both greater strength and greater heat conductivity, and drilling holes 31 at the corners of the flanges for the mess sary bolts.

As shown, the muflier is adapted for attachment to a single cylinder of an engine of radialtype and, of course, is to be so attached'that its axis will be approximately in the line of the air stream; but one mufiler may be connected through a suitable manifold to as many as three cylinders, provided that they are so timed that each cylinder completes-its scavenging stroke before the exhaust valve of the next cylinder opens.

The muffler is not only simple in construction, having few parts which are readily as sembled, but is also eliicient both as a silencer and as contributing to the e'fficiency of the engine. It produces a slight increase in the number of revolutions of the engine per minute, whereas the effect of all mulllers heretofore used is to reduce the normal speed or" the engine. And by removin the small bolts which attach the mouth of the Venturi tube to the forward conical stamping the venturi can, as already stated, be withdrawn from the casing and the whole mufl'ler opened up for cleaning of deposited carbon without removal from the engine.

It is to be understood that the muflier may of its throat and an inlet to the chamber adapted to be attached to the exhaust of an engine and to gradually spread and expand the exhaust gases and to deliver them direct- 1y into the chamber tangentially and in a thin stream extending substantially the length of the chamber, the chamber and the openings in the tube wall permitting the exhaust gases to rotate freely and to further expand within the chamber.

2. A" muflier for gas engines comprising an outer cylindrical casing, an integral Venturi tube mounted therein and connected at each end therewith by a conical stamping, regularly distributed openings in the walls of the Venturi tube to the rear of its throat, and a single inlet carried by the outer casing and arranged to receive the exhaust gases of an engine and to gradually spread and expand the same and deliver them tangentially in a thin stream through a longitudinal opening extending substantially the length of the casing.

3. A niufiier for gas engines comprising an outer casing substantially circular in cross-section, a Venturi tube mounted coaxially within the casing forming therewith an annular chamber which surrounds the venturi substantially from end to end and is closed at both its ends, an intake connecting with and adapted to support the casing, which intake spreads the exhaust gases received at its outer intake end and delivers them tangentially into the annular chamber through a narrow slit extending longitudinally oi the chamber and having an area greater than the area of the outer intake end,

and an outlet from the chamber into the Venturi tube'which is provided by a number of small regularly distributed holes formed in the rear section of the tube wall to the rear of its throat and having an'aggregate area of nlot less than the area of the inlet discharge S 11'.

4. A mufiier forges engines comprising a Venturi tube with perforationsin its walls to the rear of the throat, an annular chamber surrounding the Venturi tube which is formed by an outer casing and two like conical stampings one connectingthe mouth of theventuri wit-h the forward end of the casing and the other providing an extension of and connecting the rear end of the venturi with "the rear end of the casing, a narrow longitudinal opening in the outer casin extending substantially the length thereo and an inlet having an upper side which is shaped up from an integral tangential extension of the casing on one side of the said longitudinal opening and a lower side which is secured to the upper side along its edges and at its inner end is attached to the casin on the other side of the said longitudina opening;

5. A mufiler for gas engines comprising an outer cylindrical casing which is provided. A

with a longitudinal opening in the side thereof, two hollow conical members which at their larger ends are fitted within and secured to the opposite ends of the casing and extend forwardly therefrom, the rear member within and the forward member beyond the casing, a Venturi tube which is perforated with holes to the rear of its throat and at its rear endis fitted with a slip joint within the smaller end of the rear conical member and at its mouth is fitted within and detachably secured to the smaller end of the front conical member, and an inlet which is carried by the casing tangentially thereof longitudinal opening in its side.

CHARLES WARD 

